JP2011087336A - Stack-up configuration for wireless communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain acceptable levels of radio frequency energy while maintaining radiation efficiency of a device. <P>SOLUTION: A stack-up configuration for a wireless communication device includes a display and a keypad on a front face of a housing for the device. A battery for providing power to the components of the wireless communication device is stacked behind the display. A circuit board that holds processing and RF circuitry for the wireless communication device is stacked behind the battery, with a top surface of the circuit board adjacent the battery. Noisy circuitry on the circuit board is covered by shielding on a back surface of the circuit board. An external or internal antenna is connected to the circuit board at a feed point. The antenna is stacked behind the circuit board, that is, between a back face of the housing and the back surface of the circuit board. The location of the battery between the display and the circuit board lowers the amount of energy radiating from the wireless communication device in the concerned near field range. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

(Related application)
This application is entitled “STACK-UP CONFIGURATION FOR A WIRELESS COMMUNICATION DEVICE” and is hereby incorporated by reference in its entirety with respect to co-pending US Application No. 11 / 014,541.

(Field of Invention)
The present invention relates generally to component structures in wireless communication devices, and more particularly, to component stacking structures in wireless communication devices for reducing Specific Absorption Rate (SAR) levels.

(background)
As the wireless communication industry grows, there is a growing demand for increasingly smaller wireless communication devices. A wireless communication device may also be referred to herein as a “wireless device”, “handset”, “cell phone”, “mobile phone”, and the like. The miniaturization of wireless devices presents design challenges, including the difficulty of placing device components within a smaller volume. Additional challenges include maintaining an acceptable level of radio frequency (RF) energy radiated from the wireless device in the near field range of interest while maintaining the radiation efficiency of the device.

  When the RF module is transmitting, the power amplifier amplifies the electronic signal and broadcasts this modulated energy into the air via the antenna. The first part of this energy travels through the free space to the target destination. Another part of this energy is wasted as heat in the device. Finally, some of the energy is absorbed by objects near the device, including the user's body.

The power density around the antenna of the wireless device varies, for example, as a function of the distance from the antenna and the direction of the antenna. The field around the antenna is usually divided into two regions. The first region is a region near the antenna called a near field, and the second region is a region far from the antenna called a far field. The boundary between the two often adopts a radius R (R = 2L ² / λ, where L is the maximum dimension of the antenna and λ is the wavelength). The far field is an area where the antenna directivity diagram is independent of the distance from the transmitting antenna, for example. The near field is the region closest to the transmitting antenna and the antenna directivity diagram depends on the distance from the antenna.

  Limitations for the safe exposure of the human body to radio frequency (RF) energy emitted from wireless devices in the near field are given from the standpoint of a unit called the Specific Absorption Rate (SAR). The Specific Absorption Rate is the amount of radio frequency energy absorbed by the human body when using a wireless transmitter. The acceptable SAR level varies from country to country. U. S. The Federal Communications Commission (FCC) determines the amount of exposure allowed to RF energy from a mobile phone, a specific local (or spatial peak) SAR of 1.6 watts (1.6 W / kg) per kg tissue. Limited to level. If the wireless device is operating within these limits, the device poses no danger to the user. Therefore, compliance with applicable near field exposure limits must be considered in any mobile phone design.

  The SAR levels of various telephones change due in part to the fact that SAR is a function of many different parameters, including device shape, transmit frequency, amplifier power level, antenna position, and so on. A typical laminated structure of a prior art mobile phone 70 is shown in FIG. The telephone 70 is housed in a housing 88 having a front surface 84 and a back surface 86. The components of telephone 70 include RF and other noisy or radiating components 90 surrounded by processing circuitry (not shown) for controlling display device 72, keypad 80, and canister type shield 76. And a circuit board 74 that holds other device components (not shown). Antenna 82 is coupled to transmitters and receivers on circuit board 74 via feed points 92. A battery 78 is also housed in the housing 88 to provide power to the components of the device 70.

  Continuing with FIG. 4, the prior art laminate structure for the telephone 70 is a display device 72 on the front face 84 of the housing 88, which is laminated on the circuit board 74. May have one or more canister type shields 76 above and below the circuit board to shield the noisy components. A battery 78 is stacked under the circuit board and is usually accessible via a battery door 94 on the back 86 of the housing 88. In addition to the canister-type shield 76 covering the noisy components on the circuit board, the prior art telephone 70 requires an additional shield (not shown), referred to herein as a compliance shield, This is because the phone 70 is brought into SAR compliance as a high energy density appears just above the front face 84. This additional shielding may include metal foils, RF absorbers, metalized plastics, metal brackets, and the like.

  The shielding in the phone 70 used to comply with an acceptable SAR level is critical in phone manufacturing in terms of actual design effort, repeated compliance testing, and cost for additional compliance shielding. Continue to apply the load. The above difficulties are amplified as the telephone size is reduced. Therefore, it is desirable to continue innovation in the industry to lower the SAR level of the phone and lower the ultimate cost of the phone in design and material costs before adding compliance shielding.

(Overview)
The wireless communication device includes a housing having a back surface and a front surface for holding a display device and a keypad. A battery for powering the components of the wireless communication device is within the housing and at least partially between the display device and the front surface of the circuit board. The circuit board holds processing and RF circuitry for the wireless communication device. The back side of the circuit board holds radiating circuit components that are shielded by a canister type shield. An external or internal antenna is connected to the circuit board at the feed point. In one embodiment of the present invention, the antenna is stacked under the circuit board, that is, between the back surface of the housing and the back surface of the circuit board.

  When the battery is placed in the space between the display device and the circuit board, the battery is placed under the circuit board and compared to the traditional device stacking structure, which is accessible from the back of the housing. The Specific Absorption Rate, measured at a predetermined distance above the front, is lowered. This reduction in SAR level reduces the amount of additional compliance shielding required to comply with an acceptable SAR level. This is particularly advantageous as the size of wireless devices continues to decrease.

  The battery and display stack on the circuit board may also provide a cavity with increased volume to hold the speaker. The volume of the cavity is determined by the difference between the combined height of the battery and the display device, the width of the circuit board or the casing, and the length of the circuit board and the battery. The increased cavity volume can improve the sound quality from the speaker of the wireless communication device.

The described embodiments are to be considered in all respects only as illustrative and not restrictive. It is also understood that the invention is not limited to the specific embodiments shown and described herein, and that many rearrangements, modifications and substitutions are possible without departing from the scope of the invention. Should be. Thus, details of the invention may be gathered in part by studying the accompanying drawings below, both in terms of its construction and operation. In the accompanying drawings, like reference numerals refer to like parts.
The present invention includes the following items.
(Item 1)
An assembly stack for a wireless communication device, the assembly stack being
A main circuit board for holding a plurality of communication circuits, the main circuit board having a top surface and a bottom surface;
A battery having a battery upper surface and a battery lower surface, the battery being located on the upper surface of the main circuit board;
A display device disposed on at least a portion of the upper surface of the battery such that the battery is disposed between the main circuit board and the display device;
At least one shield located below the bottom surface of the main circuit board, the shield for shielding at least one of a plurality of communication circuits;
An assembly laminate structure comprising:
(Item 2)
Item 4. The assembly laminate structure according to Item 1, further comprising an antenna connected to the main circuit board.
(Item 3)
The assembly laminated structure according to Item 2, wherein the antenna is located below the bottom surface of the main circuit board.
(Item 4)
The assembly laminate structure according to item 2, wherein the antenna is an internal antenna having a feed point connected to the main circuit board.
(Item 5)
A housing surrounding the main circuit board, the battery, the at least one shield, and at least a part of the display device;
At least one side surface substantially perpendicular to the top surface of the main circuit board;
A battery access panel located on the at least one side, the battery access panel for removing the battery from the housing;
The assembly laminated structure according to Item 1, further comprising a housing comprising:
(Item 6)
A housing for enclosing the main circuit board, the battery, the at least one shield, and at least a part of the display device, the housing having an end surface;
A speaker in an open volume generated on the upper surface of the main circuit board and between the end surface of the housing and the laminated structure of the battery and the display device;
The assembly laminated structure according to item 1, further comprising:
(Item 7)
A wireless communication device assembly comprising:
Housing means including an upper housing surface, a lower housing surface, and at least one side surface;
At least one circuit board housed in the housing means, having a top surface and a bottom surface, for holding a processing circuit network;
Display means adjacent to the upper surface of the housing and housed in the housing means;
A battery housed in the housing and disposed between the display device and the uppermost circuit of the at least one circuit board;
A wireless communication device assembly comprising:
(Item 8)
The processing circuit network includes a radio frequency circuit network disposed at least partially on the bottom surface of the at least one circuit board, and the wireless communication device is shielding means housed in the housing, Item 8. The wireless communication device according to Item 7, further comprising shielding means for shielding the frequency network.
(Item 9)
Transceiver circuitry at least partially on the at least one circuit board;
An antenna connected to the transceiver network and housed in the housing adjacent to the at least one circuit board;
The wireless communication device according to item 7, further comprising:
(Item 10)
Item 10. The wireless communication device according to Item 9, wherein the antenna is an internal antenna.
(Item 11)
Item 10. The wireless communication device according to Item 9, wherein the antenna is an external antenna.
(Item 12)
8. The wireless communication device of item 7, wherein the battery is accessible via a side panel on the at least one side of the housing means.
(Item 13)
A method for assembling a wireless communication device in a housing, comprising:
Attaching at least one circuit board having a plurality of electrical components to the bottom of the housing, the at least one circuit board including an upper surface and a lower surface;
Mounting a battery in the housing and on an upper surface of the at least one circuit board;
Mounting a display device in the housing and on the battery;
Including a method.
(Item 14)
14. The method of item 13, further comprising attaching at least one shield to a bottom surface of the at least one circuit board for shielding at least one electrical component of the plurality of electrical components.
(Item 15)
14. The method of item 13, further comprising attaching an antenna to a lower surface of the at least one circuit board.
(Item 16)
The antenna is an internal antenna,
Attaching the internal antenna between the at least one circuit board and the bottom of the housing within the housing;
Connecting the internal antenna to a feed point of the at least one circuit board;
14. The method according to item 13, comprising:
(Item 17)
14. The method of item 13, further comprising attaching a battery door for accessing the battery to a side of the housing.
(Item 18)
14. The method of item 13, further comprising attaching a speaker to the top surface of the at least one circuit board within an open volume created between an end surface of the housing and the battery.
(Item 19)
A wireless communication device,
A power source connected to the top surface of the circuit board, supplying power to electrical components of the wireless communication device, and a first surface adjacent to the circuit board and a second substantially parallel to the first surface A power supply having
The circuit board for holding a plurality of electrical circuits including radio frequency (RF) circuitry for receiving and transmitting RF signals and processing circuitry for controlling the electrical components;
A display device connected to the circuit board on the second surface of the power supply, the display device being controlled by the processing circuit;
A wireless communication device comprising:
(Item 20)
Item 20. The wireless communication device of item 19, further comprising an antenna connected to the RF circuit by a feed on the circuit board, wherein the antenna is one of an internal antenna and an external antenna.
(Item 21)
A shield for covering the RF circuit;
Item 20. The wireless communication device of item 19, wherein the shield is connected to a bottom surface of the circuit board.

FIG. 1 is a side view of a laminated structure of an embodiment of the present invention having an external antenna. FIG. 2 is an end view of the laminated structure according to the second embodiment of the present invention. FIG. 3 is a perspective view of another embodiment of a wireless device assembly of the present invention having an internal antenna. FIG. 4 is a side view of a conventional laminated structure. FIG. 5 is a graph of the energy density of the near field for the stacked structure of the present invention compared to the near field for the stacked structure of the present invention, spaced from the front surface 84 in FIG. 4 or the front surface 6 in FIG. . FIG. 6 shows the radiation level of a prior art laminate structure relative to the surface of the user's head. FIG. 7 illustrates the reduced radiation level of one embodiment of the present invention relative to the user's head surface. FIG. 8 is a block diagram of a wireless communication apparatus according to an embodiment of a stacked structure. FIG. 9 is a circuit diagram of an apparatus network according to an embodiment of the present invention.

(Detailed explanation)
As the wireless industry expands, mobile phone manufacturers are developing innovative wireless devices that are becoming smaller and smaller in size. Due to the miniaturization of the telephone, the user's head is exposed to more radio frequency (RF) energy in the near field (where RF energy is measured by the Specific Absorption Rate (SAR) level) and more in the far field. Less radiated. Therefore, it is very difficult to reduce human exposure and improve radiation efficiency while maintaining a miniaturized telephone. The present invention addresses this challenge by presenting an innovative layered structure of components within the telephone.

  As discussed above, the prior art telephone as shown in FIG. 4 has a traditional mechanical stack from the top to the back of the telephone. A traditional laminate is a display device, such as a liquid crystal display (LCD), which can be followed by a main board, a shield and a battery on the top surface. Usually, the antenna feed point is on the main board. In contrast, the laminated structure of one embodiment is shown in FIG. The wireless device 2 is surrounded by a housing 4 having a front surface 6 and a back surface 8. The upper surface 6 of the wireless device 2 holds the display device 10 and the keypad 22. The battery 12 is housed behind the display device and above the circuit board 16. The circuit board 16 holds most of the electronic circuitry for the wireless device 2, including noisy components 24, that is, components that emit RF energy. The radiating component 24 is shielded by a shielding material 14 such as, for example, a canister, an RF absorber, a metalized plastic cover, or the like. In the illustrated embodiment of FIG. 1, the antenna 18 is an external antenna 18 having an antenna feed point 20 on the back surface 26 of the circuit board 16. The RF energy of the modulated RF signal radiates from the antenna 18 and generates a near field and a far field.

  The mechanical laminate structure of FIG. 1 reduces the amount of energy emitted in the near field of interest compared to the prior art laminate structure of FIG. In particular, the placement of the battery 12 between the display device 10 and the circuit board 16 contributes to a reduction in radiant energy in the near-field area in question. As discussed below, the simulation for the energy density distribution in free space is performed in a plane 28 adjacent to the front face 6 of the device 2. The plane 28 that is 0.5 mm above the front is also close to the position of the user's head when using the device 2.

FIG. 5 is a graph of free space energy density (J / m ³ ) distributed on the plane 28 in FIG. 4 for a traditional stack, indicated by curve 90, in FIG. 1 for the stack embodiment of the present invention. On the plane 28, it is distributed as indicated by a curve 92. Both simulations are done without including compliance shielding as discussed above. The plane 28 is 0.5 mm above the front surface. Sample simulation results taken on a plane 28 as shown in FIGS. 1 and 4 are shown for illustrative purposes only. Other simulations can yield different values for energy density, and the examples shown should not be considered as limiting embodiments of the invention. The graph shows that in the area of interest, the maximum energy density above the traditional stack of FIG. 4 is about 3.8 times the energy density above the innovative stack of FIG.

  In one sample SAR performance simulation of the prior art laminate structure of FIG. 4, the average SAR based on IEEE standard 1529 is 2.10 W / kg at 24 dBm, assuming the phone thickness from front 84 to back 86 is 22 mm. . The simulation results are taken without compliance shielding as discussed above. Therefore, in order for this particular sample prior art telephone to achieve the required 1.6 W / kg SAR standard, the device housing must include additional compliance shielding. In comparison, the innovative laminate of FIG. 1 has an average SAR of 1.58 W / kg at 24 dBm, based on IEEE-1529, at the same 22 mm thickness. In this simulation analysis, the SAR value is reduced by about 24.8% for the laminated structure of the present invention. Thus, the amount of compliance shielding required to bring a sample inventive telephone into compliance with the SAR standard is reduced. This reduction represents a reduction in design time, manufacturing time and material costs.

  6 and 7 are provided to show SAR performance as described above and are based on sample simulations. FIG. 6 shows the user's head 102 when the user places the prior art telephone 104 on his / her head 102. The Specific Absorption Rate power density “bands” A, B, C, D in units of W / kg decrease with distance from the source 104. Band A represents the area of the user's head that absorbs the highest power density. Compared to this, the SAR power density of the embodiment of the present invention is reduced as shown in FIG. As indicated by reference to bands A ', B', C ', D', the area of the user's head 102 that absorbs the highest power density is significantly smaller than that of the prior art.

  The far-field simulated radiation performance in the far field for a traditional stack of samples has a radiation efficiency of 92.84% with a directivity of 2.73 dBi and a gain of 2.41 dBi. In comparison, the stacked structure of the sample embodiment of the present invention yields a radiation efficiency of 92.86% with a directivity of 2.75 dBi and a gain of 2.43 dBi. Thus, both traditional and innovative laminates have the same radiation performance in free space. However, in the far field, the simulation results for the prior art sample next to the head show a radiation efficiency of 22.77% with a directivity of 5.98 dBi and a gain of −0.45 dBi. In comparison, the laminated structure of the sample embodiment of the present invention produces a radiation efficiency of 32.72% with a directivity of 5.89 dBi and a gain of 1.04 dBi. Thus, the innovative laminate structure has about 10% better antenna efficiency in the far field compared to the traditional laminate while the sample is held next to the human head.

  FIG. 2 shows an end view of an apparatus 30 according to another embodiment of the present invention. The laminated structure along the height axis H is such that the circuit board 36 is above the shield 38 and the external antenna 40, the battery 34 is above the circuit board 36, and the display device 32 is above the battery 34. is there. As shown, the device 30 does not require special placement of components with respect to the length axis L and the width axis W of the device 30 in order to obtain a reduction in SAR. In one embodiment of the apparatus 30 of FIG. 2, the battery 34 is accessible through a battery door 44 in the housing 42.

  FIG. 3 is a perspective view of another embodiment of a wireless device stack 50 having an internal antenna 66 connected to a circuit board 54 by a feed point 68. The battery 58 is stacked below the display device 52 and a keypad (not shown) and above the circuit board 54. The radiator and other components such as memory on the bottom surface of the circuit board 54 are shielded by a shield 56. In this embodiment, the speaker 60 is disposed in a volume 64 that is spaced from the stack of the battery 58 and the display device 52. This volume 64 improves the sound quality of the speaker 60. A microphone 62 is also shown in this space 64.

  FIG. 8 is a block diagram 110 of the components of an embodiment of the present invention showing the relative position with respect to the front and back surfaces of the housing. The display device 124 and keypad 126 on the front surface of the device 110 are controlled by the device circuitry on the circuit board 120. The speaker 128 and the microphone 130 transmit and receive audio signals to and from the device network 120. A power source 122, such as a battery, supplies power to the components of the device 110 through the circuit board 120. The antenna 116 is connected to the circuit board 120 by a feed point 118. The shield 132 covers at least a part of the network on the circuit board 120.

  FIG. 9 is a block diagram illustrating a wireless communication device 150 that may be used in connection with various embodiments described herein. However, other wireless communication devices and / or architectures may be used as will be apparent to those skilled in the art. In the illustrated embodiment, the wireless communication device 150 includes an antenna 152, a multiplexer 154, a low noise amplifier (“LNA”) 156, a power amplifier (“PA”) 158, a modulation circuit 160, a baseband processor 162, a speaker 164, A microphone 166, a central processing unit (“CPU”) 168, a data storage area 170 and a user interface 172 are included. In the wireless device 150, radio frequency (RF) signals are transmitted and received by the antenna 152. Multiplexer 154 acts as a switch and couples antenna 152 between the transmit and receive paths. In the receive path, the received RF signal is coupled from multiplexer 154 to LNA 156. LNA 156 amplifies the received RF signal and couples the amplified signal to the demodulation unit of modulation circuit 160. The demodulator strips the RF carrier signal and leaves the baseband received audio signal, which is sent from the demodulator output to the baseband processor 162. If the baseband received audio signal contains audio information, the baseband processor 162 decodes the signal, converts it to an analog signal, and sends it to the speaker 164.

  Baseband processor 162 also receives an analog audio signal from microphone 166. These analog audio signals are converted into digital signals and encoded by the baseband processor 162. Baseband processor 162 also encodes the digital signal for transmission and generates a baseband transmit audio signal that is routed to the modulator portion of modulation circuit 160. The modulator mixes the baseband transmit audio signal with the RF carrier signal to generate an RF transmit signal that is routed to the power amplifier 158. The power amplifier 158 amplifies the RF transmit signal and forwards it to the multiplexer 154 where the signal is switched by the antenna 152 to the antenna port for transmission. Baseband processor 162 is also communicatively coupled to central processing unit 168 having access to data storage area 170. Central processing unit 168 is configured to execute instructions (ie, computer programs or software) that may be stored in data storage area 170. The computer program may also be received from the baseband processor 162 and stored in the data storage area 170 or executed after reception.

  The description and drawings contained herein are specific embodiments of the present invention and are representative of the subject matter broadly contemplated by the present invention. However, the present invention includes other embodiments that will be apparent to those skilled in the art. Accordingly, the scope of the invention is limited only by the appended claims.

Claims (12)

An assembly stack for a wireless communication device comprising:
The assembly laminate structure is
A housing having a front surface, a back surface, a first side surface, and a second side surface;
A main circuit board for holding a plurality of communication circuits, wherein the main circuit board includes a top surface and a bottom surface, and at least one circuit on the bottom surface of the main circuit substrate is covered with a shield. The main circuit board,
An antenna having an antenna feed point connected to the bottom surface of the main circuit board, the antenna disposed between the bottom surface of the main circuit board and the back surface of the housing;
A battery having a battery upper surface and a battery lower surface, the battery being located on the upper surface of the main circuit board;
A display device disposed on at least a part of the upper surface of the battery, wherein the battery is disposed between the main circuit board and the display device, and the display device is disposed on the casing. A display device comprising a portion of the front surface, wherein the battery and the display device are stacked to provide an open volume;
With
The main circuit board, the battery, and the display device form the assembly stack structure, and the assembly stack structure generates near-field energy radiated from the antenna through the front surface of the housing. Reduce,
The laminated structure improves the sound quality of the device speaker by providing the open volume in the housing. The assembly laminated structure according to claim 1, wherein the antenna is an internal antenna having a feed point connected to the main circuit board. The housing is
At least one side surface substantially perpendicular to the top surface of the main circuit board;
A battery access panel located on the at least one side, the battery access panel for removing the battery from the housing;
The assembly laminate structure according to claim 1, comprising: The assembly according to claim 1, further comprising a speaker in an open volume generated on the upper surface of the main circuit board and between an end surface of the housing and a stacked structure of the battery and the display device. Laminated structure. A wireless communication device assembly comprising:
A housing including an upper housing surface, a lower housing surface, and at least one side surface;
At least one circuit board housed in the housing, comprising an upper surface and a bottom surface, and at least one circuit board for holding a processing circuit network;
A display device adjacent to the upper housing surface of the housing and housed in the housing;
A battery housed in the housing, the battery being disposed between the display device and the uppermost circuit of the at least one circuit board;
With
The at least one circuit board comprises:
A radio frequency network disposed at least partially on the bottom surface of the at least one circuit board;
An antenna connected to a feed point on the bottom surface of the at least one circuit board;
Including
The battery and the display device are stacked to provide an open volume,
The at least one circuit board, the display device, and the battery form a laminated structure included in the housing;
The wireless communication device assembly, wherein the laminated structure provides the open volume to improve the sound quality of the device speaker and reduce near field energy radiated from the antenna through the front surface of the housing. The wireless communication apparatus according to claim 5, wherein the antenna is an internal antenna included in the housing. The wireless communication device according to claim 5, wherein the antenna is an external antenna extending beyond the housing. The wireless communication device of claim 5, wherein the battery is accessible via a side panel on the at least one side of the housing. A method for assembling a wireless communication device in a housing, comprising:
The method
Attaching at least one circuit board having a plurality of electrical components to the bottom of the housing, the at least one circuit board including an upper surface and a lower surface, wherein the antenna is an antenna feed point on the lower surface Attached to the step, and
Mounting a battery in the housing and on an upper surface of the at least one circuit board;
Mounting a display device within the housing and over the battery, wherein the battery and the display device are stacked to provide an open volume;
Improving the sound quality of the device by disposing a speaker in the open volume of the housing;
Including
The stacked structure of the at least one circuit board, the battery, and the display device reduces near-field energy radiated from the antenna through the front surface of the housing. The method of claim 9, further comprising attaching at least one shield to a bottom surface of the at least one circuit board to shield at least one electrical component of the plurality of electrical components. The method of claim 9, further comprising attaching a battery door to the side of the housing to access the battery. The method of claim 9, further comprising attaching the speaker to an upper surface of the at least one circuit board within the open volume created between an end surface of the housing, the battery, and the display device.

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